TRANSPIRATION RATE OF DOUGLAS FIR TREES IN THINNED AND UNTHINNED STANDS

1980 ◽  
Vol 60 (4) ◽  
pp. 625-631 ◽  
Author(s):  
T. A. BLACK ◽  
U. NNYAMAH ◽  
C. S. TAN
Keyword(s):  
Soil Water ◽  
Transpiration Rate ◽  
Root Zone ◽  
Douglas Fir ◽  
Understory Vegetation ◽  
Diameter Growth ◽  
Tree Diameter ◽  
Evapotranspiration Rate ◽  
Sunny Weather ◽  
Extractable Soil

A procedure is described for estimating the transpiration rate of trees in stands with understory vegetation. The procedure combines soil water balance measurements of stand evapotranspiration rate with a simple vapor diffusion model that requires occasional intensive measurements of stomatal conductance of the trees and understory vegetation. Weekly average transpiration rates of 22-yr-old Douglas fir trees in a thinned stand during sunny weather in July ranged from 23.6 L∙tree−1∙d−1 when θe the fraction of extractable soil water remaining in the root zone, was 0.79 to 4.9 L∙tree−1∙d−1 when θe was 0.20. The transpiration rate of trees in the thinned stand, which contained a salal understory, was very similar to that in a nearby unthinned stand with virtually no understory vegetation. As θe decreased from slightly more than 0.8 to slightly less than 0.2, the fraction of evapotranspiration from the thinned stand due to the salal understory increased from approximately 40 to 65%. Competition for soil water by the understory was considered to be a contributing reason why tree diameter growth in the thinned stand was only slightly greater than in the unthinned stand.

Relationship of Pacific Madrone Sprout Growth to Productivity of Douglas-Fir Seedlings and Understory Vegetation

1990 ◽  
Vol 5 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Thomas F. Hughes ◽  
John C. Tappeiner ◽  
Michael Newton
Keyword(s):  
Pseudotsuga Menziesii ◽  
Secondary Succession ◽  
Douglas Fir ◽  
Understory Vegetation ◽  
Diameter Growth ◽  
Area Index ◽  
Old West ◽  
Pacific Madrone ◽  
Relationship Of ◽  
Sprout Growth

Abstract We studied the development of Pacific madrone (Arbutus menziesii) sprout clumps of various initial densities and their effect on Douglas-fir (Pseudotsuga menziesii) seedling growth and understory vegetation. Five years after density treatments, average leaf area index (LAI) of 9-year-oldmadrone sprouts ranged from 3.6-1.0 m²/m² and total aboveground biomass from 25,630-8,390 kg/ha on the high- and low-density plots, respectively. Diameter of 9-year-old Douglas-fir was inversely related to madrone LAI and ranged from about 27 mm on the high-density plots to 54 mmin the absence of madrone. Analyses of diameter growth trends also indicated that, in the absence of madrone, Douglas-fir grew significantly (P = 0.001 to 0.023) faster than in other treatments. An index of shrub, forb, and grass density was inversely related to madrone LAI, suggesting thatunderstory species are quickly excluded from young madrone stands during secondary succession. We provide equations relating the 5-year growth of 9-year-old Douglas-fir to measures of madrone density and seedling size made when the plantation was 5 years old. West. J. Appl. For. 5(1):20-24.

Estimating water fluxes in Douglas-fir plantations

1985 ◽  
Vol 15 (4) ◽  
pp. 701-707 ◽  
Author(s):  
Susan J. Riha ◽  
Gaylon S. Campbell
Keyword(s):  
Soil Water ◽  
Root Zone ◽  
Potential Evapotranspiration ◽  
Field Measurements ◽  
Douglas Fir ◽  
Root Uptake ◽  
Richards Equation ◽  
Water Fluxes ◽  
Air Temperatures ◽  
Dimensional Finite Element

A model was developed to estimate water fluxes in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations using daily measurements of precipitation and maximum and minimum air temperatures. Soil water flow was modeled using a one-dimensional finite element solution to the Richards equation, with precipitation and root uptake of water included as source and sink terms. Soil hydraulic properties varied as a function of depth. Root uptake of water was based on an analog water uptake model modified to include root resistance and cylindrical flow of water. Potential evapotranspiration was calculated assuming leaf and air temperature did not differ and assuming stomatal conductance was dependent on the vapor density deficit of the air. Model validity was tested by comparing predictions with field measurements of soil water content made in the summer of 1978 at two locations in western Washington. In general, the model predicted the observed drying of the soil. Aspects of the simulated water budget for these Douglas-fir stands considered most significant were (i) the use of soil-stored water for transpiration in the summer, (ii) the net flux of water into the root zone from deeper in the soil during the summer, (iii) the dependence of water reaching the soil in the summer on the intensity of rainfall, (iv) the large percentage of the total transpiration that occurred in spring and fall, and (v) the large amount of water moving out of the soil profile in the winter.

Extractable Soil Water and Transpiration Rate of Soybean on Sandy Soils

1907 ◽  
Vol 90 (3) ◽  
pp. 363-368 ◽  
Author(s):  
Thomas R. Sinclair ◽  
Luther C. Hammond ◽  
J. Harrison
Keyword(s):  
Soil Water ◽  
Transpiration Rate ◽  
Sandy Soils ◽  
Extractable Soil

scholarly journals Using the sensitivity of biomass production to soil water for physiological drought evaluation

2008 ◽  
Vol 3 (Special Issue No. 1) ◽  
pp. S116-S122 ◽  
Author(s):  
V. Novák
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Biomass Production ◽  
Transpiration Rate ◽  
Water Movement ◽  
Root Zone ◽  
Vegetation Period ◽  
Plant Production ◽  
Potential Transpiration

The analysis of drought as a phenomenon and the proposal of how to define and quantify the deficiency of water in soil for plants, so called physiological drought, are described. The presented approach is based on the theoretical considerations supported by empirically estimated relationships between the biomass production of a particular plant and the transpiration total of this plant during its vegetation period. This relationship is linear and is valid for particular plant and environmental conditions (nutrition, agrotechnics). Optimal plant production can be reached for maximum seasonal transpiration total, therefore the potential transpiration total corresponds to the maximum possible yield. The transpiration rate lower than the potential one leads to a biomass production decrease. This phenomenon can be used to define the physiological drought, under which the soil water content in the root zone decreases below the so called critical soil water content of limited availability for plants, under which the transpiration rate drops below its potential transpiration rate. Methodology is illustrated on the basis of the results of mathematical modelling of soil water movement in Soil – Plant – Atmosphere system, with loamy soil and maize canopy.

Method to estimate the critical soil water content of limited availability for plants

Biologia ◽  
2006 ◽  
Vol 61 (19) ◽  
Author(s):  
Viliam Novák ◽  
Ján Havrila
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Biomass Production ◽  
Transpiration Rate ◽  
Water Availability ◽  
Linear Relation ◽  
Root Zone ◽  
Limited Availability ◽  
The Relationship

AbstractThis contribution contains a proposal to estimate the critical soil water content of limited availability for plants, below which transpiration starts to decrease due to limited water availability for roots, which is frequently noted as “the point of limited soil water availability”. The method is based on the fact, that soil water content at which transpiration rate is starting to decrease is followed by the biomass production decrease. The method is using the relationship between the relative transpiration and the average soil water content of the soil root zone, and the linear relation between biomass production and transpiration, published earlier.

Belowground competition influences growth of natural regeneration in thinned Douglas-fir stands

2008 ◽  
Vol 38 (12) ◽  
pp. 3085-3097 ◽  
Author(s):  
Warren D. Devine ◽  
Timothy B. Harrington
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Nitrogen Concentration ◽  
Nitrogen Deficiency ◽  
Douglas Fir ◽  
Understory Vegetation ◽  
Detectable Effect ◽  
Belowground Competition ◽  
Overstory Trees

Using a factorial combination of understory removal and trenching treatments, we examined the influences of belowground competition from understory and overstory vegetation on growth of naturally established Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii) saplings in thinned stands of Douglas-fir on moderately productive, glacially derived soils near Tacoma, Washington. Under limited light (26% ± 16% of full sun), sapling height and diameter growth were significantly reduced by belowground competition from overstory trees. Regardless of presence or absence of belowground competition from trees, understory vegetation did not have a detectable effect on sapling growth. Nitrogen deficiency in saplings was not detected in the presence of belowground competition: where tree roots were excluded, foliar nitrogen concentration and content increased without an increase in foliar mass. Belowground competition from overstory trees had a greater negative effect on growing season soil water content than did understory vegetation. Under the conditions of restricted light availability in this study, limitations in soil water content from competition had a strong growth-limiting effect on Douglas-fir regeneration. As potential canopy trees in a future uneven-aged stand, this sapling cohort would benefit from root gaps created during harvests.

Transpiration and leaf water potentials of wheat in relation to changing soil water potential

1977 ◽  
Vol 28 (3) ◽  
pp. 355 ◽  
Author(s):  
KA Seaton ◽  
JJ Landsberg ◽  
RH Sedgley
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Transpiration Rate ◽  
Water Conservation ◽  
Root Zone ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Water Potentials

Changes in the transpiration rate of wheat in drying soils were followed in experiments in which plants were grown in two small weighable lysimeters in a glasshouse. Hourly measurements of soil water potential (Ψs) were made at three depths in each lysimeter. The water potential of flag leaves was measured with a pressure chamber, and stomatal resistance with a pressure drop porometer. Data on root densities and distribution were also obtained. Transpiration rates fell below estimated potential levels when the average value of Ψs in the root zone was reduced to –1 to –5 bars, depending on soil storage, root distribution and potential transpiration rate. From this point Ψs fell rapidly in the surface layers, more slowly at depth. It was found that accurate calculations of daily water uptake could be made from changes in soil water content. The minimum value of leaf water potential (�1 )attained each day declined progressively through the drying cycle, but there was evidence that stomatal resistance (rs) is not uniquely related to Ψ1; initial stomatal closure occurred at Ψ1, values which decreased from –11 to –25 bars as drying progressed. This adaptive mechanism is related to changes in osmotic potential of the leaves. Whole plant resistances (Rp), derived from leaf water potentials and fluxes through individual stems, increased as stem populations increased. In the high population lysimeter Rp decreased from 300 to 100 bar sec mm-3 as canopy transpiration rates increased from 1.5 to 4.5 x 10-4 mm sec-1. In the low population lysimeter Rp decreased from 70 to 30 bar sec mm-3 as transpiration increased from about 2.2 to 4.5 x 10-4 mm sec-1. The higher resistances appear to confer significant advantages in terms of water conservation and adaptation to drought.

scholarly journals Transpiration rate response to water deficit during vegetative and reproductive phases of upland rice cultivars

2011 ◽  
Vol 68 (1) ◽  
pp. 24-30 ◽  
Author(s):  
Alexandre Bryan Heinemann ◽  
Luís Fernando Stone ◽  
Nand Kumar Fageria
Keyword(s):  
Water Stress ◽  
Soil Water ◽  
Water Deficit ◽  
Transpiration Rate ◽  
Root Zone ◽  
Rice Yield ◽  
Upland Rice ◽  
Growth Stages ◽  
Rice Cultivars ◽  
Potential Yield

Water deficit is one of the most important abiotic stress limiting upland rice yield in the "Cerrado" region of Brazil. Selecting drought tolerant cultivars is an important strategy to overcome this constraint. Two greenhouse experiments were conducted at Santo Antônio de Goiás, state of Goiás, Brazil, to compare the response of normalized transpiration rate (NTR) of three modern (BRS Primavera, BRSMG Curinga and BRS Soberana) and one traditional (Douradão) upland rice cultivars to soil water deficit during the vegetative and reproductive growth stages. This information will support breeding strategies to improve rice yield in a drought-prone target population environments (TPE) in Brazil. NTR and the total fraction of transpirable soil water (FTSW) were calculated, plotted and adjusted according to a sigmoid non-linear model. The p factor, defined as the fraction of available soil water that can be removed from the root zone before water deficit occurs, was calculated by assuming that it occurs when NTR is equal to 0.95. Modern cultivars had a higher value of p for the reproductive phase than for the vegetative phase. In addition, these cultivars are better adapted to express their potential yield in regions with low intensity and occurrence of water stress and the traditional cultivar is enable to better support adverse conditions of water stress. It can be concluded that there is need to precisely characterize drought patterns in TPEs. This information can focus the breeding program to improve drought tolerance in modern upland rice cultivars.

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